Right ventricular contractility at rest and during exercise in COPD

Rationale: COPD patients show a limited stroke volume response to exercise. This is thought to be due to an increased right ventricular (RV) afterload. Whether an impairment to increase RV contractility contributes to the impaired stroke volume response is unknown. Therefore, the aim of this study is to determine whether RV contractility changes during exercise in COPD patients. Methods: Nine patients with COPD (GOLD II-IV) underwent right heart catheterisation and subsequently cardiac MRI at rest and during submaximal exercise. With cardiac MRI RV volumes were measured. During right heart catheterisation RV pressure curves were continuously measured. As a measure of contractility, the maximum rate of rise of RV pressure (dP/dt max ) was obtained from an averaged RV pressure waveform over several respiratory cycles, see figure 1. Then, dP/dt max was normalized for RV end-diastolic volume, i.e. dP/dt max /EDV (1). Results: In all patients dP/dt max /EDV increased with exercise. At rest mean dP/dt max /EDV was 3.6±1.3 mmHg/s/ml, while during exercise it was 6.9±3.7 mmHg/s/ml (p=0.001). RV end-systolic volume did not change with exercise. Conclusions: COPD patients show an increase in RV contractility. The increase in contractility does not result in a decrease in RV end-systolic volume. Reference: 1Kass DA, Maughan WL, Guo ZM, et al. Circulation 1987 Dec; 76(6):1422-36.